Magic & Divine

If all the planes of existence in Dungeons & Dragons float somewhere in a 'fabric of reality', then the Netherscape is this very fabric they float in. This means that the Netherscape is connected to each of these plains, and so is infused with the magic of all of them. This makes te Netherscape one of the places where things like a spellplague would affect everyone, even those that don't use it. During the last spellplague the Netherscape was in such turbulence that many lesser beings are now still trying to step aside from their original purpose. It had an effect on the stronger among the beings too, they lost a margin of their power, only to be regained by bargains and favors. During the last decade many mortals in the forgotten realms have made, accepted, tried to back out of, and thrived with bargains made with the fae. The Sidhe amassed more power, and in doing so have attempted to regain the balance of power as it was before the spellplague.

The gods of the forgotten realms have always been aware of the connection each realm had to the Netherscape, and have tried many times to enter its space and enact their influence. However the Queens of fairy, and a few other mythical beings in the same league, would not have it. So they created a barrier. They had seen what the gods did to the Material plane. Only when a god makes a bargain with a select few fae in the Netherscape, can they enter the world and act, for the limited time given. Or they had to be incredibly sneaky, for there is one place where they might attempt to enter...

Magic Mechanics

Magic infuses the entire Netherscape, which makes it easy to tap into. However, due to the various creatures that use it and sometimes abuse it. It has some variations on what most are used to in the Material plane.

Illusion Magic

In fairy, which is technically the most prominent area in the Netherscape, illusion magic is the strongest. This means that the use of such magic is always cast as if it was used as one spellslot higher. Cantrips, are unaffected.

Healing magic

Healing magic requires imagination of the healer, usually this means a few gestures and words done, but in the Netherscape however, this is done by a combination of smaller spells connection each cell of a body back into place. Given the amount of different beings and their vastly different anatomy, this becomes incredibly hard to do. This is something usually only possible for the most powerful creatures in the world.
For this reason, every healing spell, regardles of spell level, heals only half the amount, and requires a medicine check where DC is the character's intelligence modifier + proficiency bonus + 8. On a success, the spell heals half the rolled amount, on a failure the spell leaves a scar, leaving the creature that receives the healing with 1 fewer maximum hitpoints.

Divine magic

Clerics, paladins and some subclasses of other professions are severely affected by the lack of their connection to whatever deity they follow. Either they simply cannot preform their magic and other divine abilities, or they are so heavilly limited in their capabilities that it renders them useless. There are a few gods that live in the Netherscape, but these are generally only followed by indiginous creatures. This can ofcourse be discussed with your GM.

Patrons

Warlocs need a patron, if they had a patron on the mortal plane, there are limitations to which patron can reach out into the Netherscape. Some have no trouble reachig out, and others are kept outside with all the other deities and beings of power. see the professions for available warlock classes.
If your patron was one of the ones not available, you will have no powers until you make a bargain with a Sidhe powerful enough to allow that creature access for as long as you roam this realm.